EP1265941B1 - Aqueous coating agents for baking enamels with a high solid content - Google Patents

Description

The present invention relates to novel aqueous coating compositions for baking finishes, in particular for the production of hard, elastic, solids-rich fillers with very good stone chip protection and their use for coating metals, plastics, wood and glass.

In recent years, the importance of aqueous paints and coatings has risen sharply due to ever stricter emission guidelines with respect to the solvents released in the paint application. Although aqueous coating systems are already available for many applications, they often can not fully achieve the high quality level of conventional, solvent-borne coatings in terms of solvent and chemical resistance or even elasticity and mechanical strength. In particular, no polyurethane-based coating agents to be processed from an aqueous phase have hitherto been known, which fully meet the high requirements of the practice of hard but simultaneous elastic fillers with high solids content for coating automobile bodies with respect to film hardness, impact resistance, resistance to chipping and resistance to water and chemicals.

This finding applies both to GB-A 1 444 933, EP-A 0 061 628 and DE-A 2 359 613, which deal with the hydrophilic modification of aromatic polyisocyanates, and also to DE-A 4 001 783 , which deals with specific anionically modified aliphatic polyisocyanates, as well as for the systems of DE-A 2 456 469, DE-A 2 814 815, EP-A 0 012 348 and EP-A 0 424 697, which are deal with aqueous Einbrennbindemitteln based on blocked polyisocyanates and organic polyhydroxyl compounds. The systems based on carboxyl-containing polyurethane prepolymers with capped isocyanate groups in accordance with DE-A 2 708 611 or the blocked, water-soluble urethane prepolymers according to DE-A 3 234 590 are also largely unusable for the stated field of application. Significant progress in terms of elasticity and solvent, water or chemical resistance can be achieved with the systems of DE-A 4 221 924, which describes combinations of specific, blocked, water-soluble or dispersible polyisocyanate mixtures and special, water-soluble or dispersible polyhydroxyl compounds. Further improvements in the required baking temperature or reactivity of stoving enamels can be achieved if water-dilutable or water-dispersible Polyisocyanatvernetzer be used with pyrazoles as blocking agents, such as. As described in WO 97/12924 and EP-A 0 802 210.

The solids content, including binders, crosslinkers, additives, pigments and fillers, of these aqueous fillers described and in some cases used in practice is generally between 47 and 50, with a maximum of 53% by weight, at processing viscosity. However, it is desirable in this context, a much higher solids content to significantly improve the application efficiency in the application. Furthermore, a much higher hardness for a better sandability of the filler is required, while good elasticity properties should guarantee a high stone chip protection level.

• I) speziellen in Wasser dispergierten blockierten Polyisocyanaten,
• II) in Wasser löslichen oder dispergierbaren Polyhydroxylverbindungen,
• III) gegebenenfalls in Wasser löslichen oder dispergierbaren Vernetzerharzen und
• IV) gegebenenfalls weiteren in Wasser löslichen oder dispergierbaren Substanzen.

As has now surprisingly been found, it is possible to produce from Einbrennfüllern to be processed from aqueous phase, in addition to the requirements met by previous fillers in practice have a higher solids content and after firing coatings with very high hardness but at the same time very good antislip properties give, if Binder selected combinations of the type described in more detail below are used. The stoving lacquers according to the invention consist of:

• I) specific water-dispersed blocked polyisocyanates,
• II) water-soluble or dispersible polyhydroxyl compounds,
• III) optionally water-soluble or dispersible crosslinker resins and
• IV) optionally other water-soluble or dispersible substances.

By using these novel binder mixtures according to the invention in aqueous baking finishes, very high solids contents can be achieved. Thus, an increase in the order efficiency and fertility is given. In the case of surfacer applications, coatings are obtained in which the hardness and thus also the sandability and the topcoat level are markedly improved in comparison with the prior art.

• I) speziellen in Wasser dispergierten blockierten Polyisocyanaten,
• II) in Wasser löslichen oder dispergierbaren Polyhydroxylverbindungen,
• III) gegebenenfalls in Wasser löslichen oder dispergierbaren Vernetzerharzen und
• IV) gegebenenfalls weiteren in Wasser löslichen oder dispergierbaren Substanzen,

dadurch gekennzeichnet, dass die Komponente I) aus

• A) 40 bis 80 Gew.-% einer oder mehrerer Polyisocyanatkomponenten,
• B) 10 bis 40 Gew.-% eines oder mehrerer im Sinne der Isocyanat-Additionsreaktion monofunlaioneller Blockierungsmittel für Isocyanatgruppen,
• C) 1 bis 30 Gew.-% eines oder mehrerer Hydrophilierungsmittel,
• D) gegebenenfalls weiteren Vernetzersubstanzen und
• E) gegebenenfalls üblichen Zusatzmitteln besteht,

mit der Maßgabe, dass die Komponente I) entweder nach einem Direktdispergierverfahren oder nach dem Phasenumkehrverfahren mittels einer Dispergiervorrichtung mit hoher volumenbezogener Dispergierleistung hergestellt wurde und eine mittlere Teilchengröße der Dispersionspartikel von 0,05 bis 10 µm, vorzugsweise 0,1 bis 5 µm, insbesondere 0,15 bis 2,5 µm und besonders bevorzugt 0,2 bis 1,5 µm Teilchendurchmesser aufweist.The invention relates to binder mixtures for aqueous baking finishes of:

• I) specific water-dispersed blocked polyisocyanates,
• II) water-soluble or dispersible polyhydroxyl compounds,
• III) optionally water-soluble or dispersible crosslinker resins and
• IV) optionally further water-soluble or dispersible substances,

characterized in that the component I)

• A) 40 to 80% by weight of one or more polyisocyanate components,
• B) 10 to 40 wt .-% of one or more in the sense of the isocyanate addition reaction monofunlaioneller blocking agent for isocyanate groups,
• C) 1 to 30% by weight of one or more hydrophilicizing agents,
• D) optionally further crosslinker substances and
• E) optionally conventional additives,

with the proviso that the component I) was prepared either by a direct dispersion method or by the phase inversion method by means of a dispersing device with high volume dispersion performance and an average particle size of the dispersion particles of 0.05 to 10 .mu.m, preferably 0.1 to 5 .mu.m, in particular 0 , 15 to 2.5 microns and more preferably 0.2 to 1.5 microns in particle diameter.

For the preparation of the invention essential dispersions I) by dispersing reach dispersing devices with high volume dispersion performance, such as. B. Druckentspannungshomogenisierdüsen, for use.

Corresponding dispersing machines are z. B. from Formation of Emulsions, in P. Beche, Encyclopedia of Emulsion Technology, Vol. 1, New York, Basel, Decker 1983 known, but have not yet been used for the preparation of such aqueous dispersions of aqueous Einbrennfüller.

Dispersing machines are selected according to the size of the volume-related power. For the preparation of finely divided dispersions (about 1 micron particle diameter) dispersing machines with high volume-related services are required, for. B. high pressure homogenizers. With rotor / stator machines, finely divided dispersions can no longer be produced well. The jet disperser described in EP-A 0 101 007 is a special pressure release nozzle, which has a much higher efficiency than high-pressure homogenizers. Even at 50 bar homogenization pressure particle size distributions are achieved with the jet disperser, for which one needs in the high-pressure homogenizer 200 bar.

With the jet disperser as dispersing device, finely divided dispersions, both continuously and discontinuously, can be produced particularly advantageously.

According to the invention, the aqueous dispersion can be converted by phase inversion of a water-in-oil emulsion in an oil-in-water emulsion.

The aqueous dispersions I) prepared according to the invention, which are essential to the invention, can be used in combination with the components II), III) and, if appropriate, IV) for stoving on any heat-resistant substrates, e.g. as filler, base coat or topcoat for the production of single-coat and / or multi-coat paints, for example in the automotive sector. The preferred use is in the filler area.

Component A) of dispersion I) which is essential to the invention comprises polyisocyanates containing aliphatic and / or cycloaliphatic biuret, isocyanurate, urethane, uretdione, allophanate and / or iminooxadiazinedione groups. It is also possible to use any desired mixtures of various polyisocyanates and polyisocyanates which contain several of the groupings mentioned. For the preparation of the polyisocyanates, it is possible to use the known aliphatic and / or cycloaliphatic diisocyanates from which the polyisocyanates are prepared by known processes, e.g. Trimerization, allophanatization, urethanization, biuretization. Preferably, use 1,6-diisocyanatohexane (HDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 2,4- and / or 2,6-diisocyanato-1-methylcyclohexane and 4,4'-diisocyanatodicyclohexylmethane (®Desmodur W, Bayer AG). Isocyanurate, biuret and / or urethane-containing polyisocyanates based on 1,6-diisocyanatohexane, isophorone diisocyanate and ®Desmodur W are preferably used for the preparation of component A).

As blocking agent B) it is possible to use the known monofunctional blocking agents, for example malonic esters, acetoacetic esters, lactams, oximes, pyrazoles, triazoles, imidazoles, amines or any desired mixtures of these classes of compounds. Preference is given to blocking agents which are in the temperature range split off to 180 ° C, in particular to 160 ° C. Preference is given to butanone oxime, cyclohexanone oxime and / or 3,5-dimethylpyrazole.

As hydrophilicizing agent C) internal emulsifiers, external emulsifiers or any mixtures of these compounds are used.

Useful internal emulsifiers include nonionic-hydrophilic structural components containing ethylene oxide units and / or (potentially) anionic structural components containing carboxyl groups.

The nonionically hydrophilic synthesis components are compounds which have one or two isocyanate-reactive groups, in particular hydroxyl groups, per molecule. The polyether chains of these compounds consist of at least 50% by weight, preferably 100% by weight, of ethylene oxide units, it also being possible for propylene oxide units to be present in addition to these, in accordance with the statements made. Suitable such nonionic hydrophilic structural components are, for example, monofunctional polyethylene glycol monoalkyl ethers having molecular weights of from 350 to 3,000. The molecular weight is preferably between 500 and 1,000.

As (potentially) anionic structural components are compounds having at least one isocyanate-reactive group. Preferably, these compounds are at least one, preferably one or two hydroxyl-containing carboxylic acids or salts of such hydroxycarboxylic acids. Suitable such acids are, for example, 2,2-bis (hydroxymethyl) alkanecarboxylic acids such as dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid or 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, hydroxypivalic acid or mixtures of such acids. Dimethylolpropionic acid and / or hydroxypivalic acid are particularly preferably used. The free acid groups, especially carboxyl groups, represent the above-mentioned "potentially anionic" groups, while those by neutralization salt-like groups obtained with bases, in particular carboxylate groups, are the "anionic" groups mentioned above. For the solution or dispersion in water, at least partial neutralization of the carboxyl groups is necessary. In general, the carboxyl groups are at least 50% neutralized, wherein optionally also an excess of neutralizing agent can be used.

As external emulsifiers, conventional emulsifiers or dispersants, as used e.g. by Johann Bielmann in Lackadditive, WILEY-VCH Verlag GmbH Weinheim, New York, Chichester, Brisbane, Singapore, Toronto 1998, pages 87-92. Particularly suitable substances are, for example, adducts of ethylene oxide and, optionally, propylene oxide with hydrophobic starter molecules, e.g. Nonylphenol, phenol / styrene condensates and long-chain, optionally branched, alcohols, such as lauryl alcohol or stearyl alcohol. Also ionic compounds of this type, such as ethylene oxide and optionally propylene oxide units containing sulfuric or phosphoric ester salts, such as. As described in WO 97/31960 are suitable.

The optionally used additional crosslinker component D) are substances which lead to a curing of the coatings according to the invention by chemical reaction with the hydroxyl groups of component II). To name a few examples are amino resins, z. For example, corresponding melamine derivatives such as alkoxylated melamine resins or melamine-formaldehyde condensation products (e.g., FR-A 943,411, "The Chemistry of Organic Film Formers," pages 235-240, John Wiley & Sons Inc., New York 1974 ) and conventional crosslinking agents, eg with alcoholic hydroxyl reactive epoxides, carboxylic anhydrides, phenolic resins, resole resins, urea resins or guanidine resins or mixtures thereof.

The customary additives E) which may be used are, for example, neutralizing agents, catalysts, auxiliaries and / or additives, such as wetting and dispersing agents, degassing agents, anti-settling agents, leveling agents, radical scavengers, antioxidants, UV absorbers, thickeners, low levels of solvents and biocides.

The production of the invention essential dispersion I) takes place in several stages, wherein the proportions of the reactants are chosen so that the equivalent ratio of isocyanate groups of component A) to isocyanate-reactive groups of component B) and optionally C) at 1: 0.5 to 1: 2, preferably 1: 0.8 to 1: 1.2 and more preferably 1: 0.9 to 1: 1.

If internal emulsifiers are used as component C), hydroxyl groups which are reactive toward isocyanate groups are present. Here, the proportions of the reactants to be used in the preparation of the invention essential dispersion I) are chosen so that the equivalent ratio of isocyanate groups of component A) to isocyanate-reactive groups of components B) and C) at 1: 0.5 to 1: 2, preferably at 1: 0.8 to 1: 1.2 and more preferably at 1: 0.9 to 1: 1.

When using nonionic hydrophilic structural components, the amount of component C) is such that 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, of within the obtained invention essential dispersion I) at within and / or laterally arranged polyether chains incorporated ethylene oxide units (calculated as C ₂ H ₄ O, molecular weight = 44) are present.

When (potentially) anionic synthesis components are used, component C) is used in such an amount that 0.1 to 5% by weight, preferably 0.5 to 1.5% by weight, in the resulting inventive dispersion I) is present. , on chemically fixed carboxyl groups (calculated as COOH, molecular weight = 45).

In the case of using external emulsifiers as component C) there are no isocyanate-reactive groups. Here, the proportions of the reaction partners are chosen so that the equivalent ratio of isocyanate groups of component A) to isocyanate-reactive groups of components B) at 1: 0.8 to 1: 1.2, preferably at 1 for the preparation of the inventive dispersion I) : 0.9 to 1: 1. The amount used of the external emulators C) based on the total amount of components A), B) and C) is 1 to 10 wt .-%, preferably 3 to 7 wt .-% and particularly preferably 4 to 6 wt .-% ,

For the preparation of component I), the polyisocyanate A) is reacted in any order or simultaneously with the blocking agent B) and optionally an internal hydrophilicizing agent C) in the above-stated NCO / OH equivalent ratio. If no internal hydrophilicizing agent is used, before, during or after the reaction of components A) and B) in the NCO / OH equivalent ratio indicated above, the admixing of an external emulsifier C) in the quantitative ratio given above.

The reactions are generally carried out in a temperature range from 20 to 140 ° C, preferably at 70 to 120 ° C, wherein in particular the reaction with (potentially) anionic synthesis components C) is carried out under mild conditions to prevent the carboxyl group reacted with the isocyanate groups.

The reactions can be carried out solvent-free or in an inert solvent. The reaction is preferably in such inert solvents as can be completely or partially removed from the aqueous phase of a dispersion by vacuum distillation after the emulsification step. Examples which may be mentioned are ketones, such as acetone and methyl ethyl ketone, and esters, such as ethyl acetate and butyl acetate, and aromatics, such as toluene and xylene. Particularly preferred is the reaction in methyl ethyl ketone.

After completion of the reaction, if a hydrophilization has taken place with a (potentially) anionic synthesis component C), an at least partial neutralization of the incorporated carboxyl groups takes place. The addition of the requisite neutralizing agent can be carried out before, during or after the dispersing step. Suitable bases for this purpose are ammonia, amines, e.g. N-methylmorpholine, dimethylisopropanolamine, triethylamine, N, N-dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, triisopropylamine, 2-diethylamino-2-methyl-1-propanol or mixtures of these and other neutralizing agents. Also suitable but less preferred neutralizing agents are alkali or alkaline earth hydroxides, e.g. Sodium hydroxide, lithium hydroxide or potassium hydroxide. Preferred neutralizing agent is N, N-dimethylethanolamine.

To prepare the aqueous suspension, the organic solution of the reaction product of components A), B) and optionally C) is mixed with water. This is done either by the Direktdispergierverfahren, wherein the organic phase is dispersed in the aqueous phase, or by the phase inversion method, wherein an initially present water-in-oil emulsion is converted into an oil-in-water emulsion. This is done with the aid of a dispersing device with a high volume-based dispersing capacity. These may be, for example, cage rotors, dissolvers, rotor / stator mixers, pressure relief nozzles, preferably jet dispersers, the volume-related dispersing power for the dispersing process being 1 to 10 ⁸ W / cm ³ , preferably 1 to 5 × 10 ⁷ W / cm ³ and more preferably 1 to 3 x 10 ⁷ W / cm ³ . The average particle size of the particles of the aqueous dispersion or suspension is 0.05 to 10 .mu.m, preferably 0.1 to 5 μ, in particular 0.15 to 2.5 microns and more preferably 0.2 to 1.5 microns. In order to obtain special particle size distributions, it makes sense to disperse in several stages at a defined volume-related power.

It has proven to be advantageous to first prepare a preemulsion by means of a stirrer or dissolver prior to the dispersion process through the jet disperser and then to supply this preemulsion to the jet disperser. In the preparation of the dispersions or emulsions, an amount of water is used that 20 to 75 wt .-%, preferably 30 to 70 wt .-% and particularly preferably 35 to 70 wt .-% dispersions or emulsions of Inventive binding agent I) result. After completion of the addition of water, the solvent, preferably in vacuo, removed by distillation.

The dispersion can be carried out in a wide temperature range both at low temperature, such. B. 10 ° C, as well as at high temperature to well above the melting point of the polymer mixture, such as. B. 150 ° C, take place. Due to the reactivity of the binder systems, only a short-term temperature load in the range of seconds is possible at such high temperatures.

The optionally used further crosslinker substances D) and the customary additives E) can be added to the organic solution of the reaction product of the components A), B) and optionally C) before the dispersion. In the case of water-soluble or dispersible substances D) and E), these may also be added to the aqueous phase after dispersion and distillation.

The polyhydroxyl component II) is, for example, water-soluble or dispersible polyhydroxyl compounds of a number average molecular weight Mn of 1,000 to 100,000, preferably 2,000 to 50,000, determinable by gel permeation chromatography (standard polystyrene), which is known per se from the chemistry of polyurethane coatings the polyhydroxyl compounds have a content of hydrophilic groups which is sufficient for their solubility or dispersibility in water, in particular polyether chains having carboxylate groups and / or ethylene oxide units. In principle, however, the use of itself is not possible sufficiently hydrophilic polyhydroxyl compounds in admixture with external emulsifiers.

As component II), polyhydroxy polyesters, polyhydroxy polyethers, polyhydroxy polyurethanes, polyhydroxycarbonates, urethane-modified polyester polyols, urethane-modified polyether polyols, urethane-modified polycarbonate polyols or hydroxyl-containing polymers, i. the known polyhydroxypolyacrylates. However, mixtures of said polyhydroxyl compounds, or prepared in situ, given grafted, representatives of combinations of these polyhydroxy compounds, such. B. Polyesterpolyacrylatpolyole, Polyetherpolyacrylatpolyole, Polyurethanepolyacrylatpolyole, Polyesterpolyurethane, Polyetherpolyurethane, Polycarbonatpolyurethane and Polyetherpolyester or their mixtures as component II) are used.

The polyacrylate polyols are known per se copolymers of simple esters of acrylic and / or methacrylic acid, wherein in order to introduce the hydroxyl groups hydroxyalkyl esters such as 2-hydroxyethyl, 2-hydroxypropyl, 2-, 3-, or 4-hydroxybutyl this Acids are used. For the introduction of carboxyl groups, which can be neutralized with amines for conversion into carboxylate groups, e.g. Acrylic and / or methacrylic acid. Possible further comonomers are olefinically unsaturated compounds, such as. As vinyl aromatics, acrylonitrile, Maleinsäuredi (cyclo) alkyl esters, vinyl esters, vinyl ethers u. s. w ..

On the one hand, the polymers can be prepared directly in water with the aid of emulsifiers, resulting in emulsion copolymers which are also called "primary dispersions". On the other hand, the preparation in organic solvents and, after introduction of ionic groups, subsequent conversion into the aqueous phase is possible, whereby so-called "secondary dispersions" are obtained.

Suitable polyether polyols are the ethoxylation and / or propoxylation products of suitable 2- to 6-valent starter molecules known per se from polyurethane chemistry, such as e.g. Water, ethylene glycol, propanediol, trimethylolpropane, glycerol, pentaerythritol and / or sorbitol.

Examples of suitable polyesterpolyols are, in particular, the reaction products of polyhydric alcohols known per se in polyurethane chemistry, for example of alkane polyols of the type just mentioned by way of example with substancial amounts of polycarboxylic acids or polycarboxylic anhydrides, in particular dicarboxylic acids or dicarboxylic acid anhydrides. Suitable polycarboxylic acids or polycarboxylic acid anhydrides are, for example, adipic acid, phthalic acid, isophthalic acid phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic acid, maleic anhydride, their Diels-Alder adducts with cyclopentadiene, fumaric acid or dimeric or trimeric fatty acids. In order to set specific molecular weights or functionalities of the polyester polyols, there is also the possibility of using monofunctional alcohols, such as. B. 2-ethylhexanol or cyclohexanol and / or monofunctional carboxylic acids, such as. For example, 2-ethylhexanoic acid, benzoic acid or cyclohexane carboxylic acid. In the preparation of the polyester polyols, of course, any mixtures of mono- and polyfunctional alcohols or any mixtures of mono- and polyfunctional carboxylic acids or carboxylic anhydrides can be used.

The preparation of the polyester is carried out by known methods, such as z. B. in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 2, G. Thieme Verlag, Stuttgart, 1963, pages 1 to 47 are described.

The optionally required hydrophilic modification of these polyester polyols is carried out by methods known per se, as disclosed, for example, in EP-A 0 157 291 or EP-A 0 427 028. The water-soluble or dispersible urethane-modified polyesters described in these publications are According to the invention as component II) particularly suitable. Particularly preferred as component II) are urethane-modified polyester resins, as described in DE-A 42 21 924. Also suitable but less preferred are the described in DE-A 38 29 587, water-soluble or dispersible hydroxyl-containing polyacrylates.

As polyfunctional crosslinking resins III) come both water-soluble or dispersible blocked polyisocyanates as well as water-soluble or dispersible amino resins such. B. melamine or urea resins, into consideration. In principle, the water-soluble or dispersible polyisocyanates are suitable, as they have also been mentioned in the prior art. However, particularly suitable are the water-soluble or dispersible blocked polyisocyanates which are described in DE-A 42 21 924 and DE-A 198 10 660.

It is also possible to use already finished mixtures of representatives of components II) and III) as a combination partner for the component I) essential to the invention. Such finished mixtures are already in practical use due to their good storage stability at room temperature.

As further, water-dispersible substances IV), for example, epoxy resins, phenolic resins, polyamine resins, low molecular weight Epoxyvernetzer and low molecular weight Polyaminvernetzer can be used.

For the preparation of ready-to-use coating compositions, in particular fillers, the invention essential special dispersions I) with the polyhydroxyl compounds II), optionally the crosslinkers III) and optionally representatives of component IV) are mixed. The mixing ratio with respect to components I) to III) is in the range from 50: 45: 5 to 5:45:50 wt.%, Preferably 45:45:10 to 10:45:45 wt.% And particularly preferably 40: 45:15 to 15:45:40 wt .-% based on the solid. Representatives of component IV) may optionally in proportions up to 20 wt .-%, preferably 10 wt .-%, based on the solid, are used. Particular preference is given to using only mixtures of components I) and II) and optionally III). The one-component binders obtained in this way are generally storable for as long as desired. Optionally used auxiliaries and additives of the coating technology, such as pigments, fillers, leveling agents, wetting agents and dispersants, blasenverhindemde agents, catalysts u. Like. Can the aqueous binder or binder mixture and / or the individual components I), II) and optionally III) and IV) are added. It is of particular advantage to process the individual components I), II) and optionally III) and IV) or I) and the mixture of II) and optionally III) with auxiliaries, pigments and fillers to ready-to-use pastes, which then arbitrarily within the above limits can be mixed with each other. In this way, very special properties can be achieved for special requirements. There is also the possibility of some additives, such. B. leveling agents or catalysts, the component I) before their dispersion in water.

The one-component coating compositions containing the dispersions I) according to the invention can be prepared by any of the methods of coating technology, such as e.g. Spraying, brushing, dipping, flooding or with the help of rollers and squeegees, on any heat-resistant substrates one or more layers are applied.

By way of example, coatings on metal, plastic, wood or glass are obtained by curing the paint film at 80 to 220 ° C., preferably 100 to 200 ° C. and particularly preferably 120 to 180 ° C.

The binders of the invention are preferably suitable for the production of coatings and coatings on steel sheets, such as those used for example for the production of vehicle bodies, machines, panels, barrels or containers. They are preferably used for the production of Automobilfüllem. The paint films generally have a dry film thickness of 0.01 to 0.3 mm.

The binders of the present invention provide long lasting surface protection, as demonstrated in the Examples. In particular, the surprisingly high stone chip resistance combined with high film hardness, which are in themselves contradictory properties, should be emphasized. This makes the binders outstandingly suitable for applications where good stone chip protection coupled with high paint film hardness is required.

The particular advantage of the novel aqueous binder is, in addition to their high stability during storage both at room temperature and at slightly elevated temperatures of 30 to 60 ° C, the particularly high solids content to be achieved of ≥ 55 wt .-%, which of previously known aqueous binders in all rule is not reached is not reached.

The following examples illustrate the invention without, however, limiting it.

Examples

All percentages are by weight unless otherwise stated.

Example 1: Preparation or Description of the Starting Materials 1.1. Polyisocyanate component A1)

In a 2-liter four-necked flask equipped with stirrer, gas inlet tube, internal thermometer, dropping funnel and reflux condenser, 1332 g of isophorone diisocyanate (IPDI) are placed under nitrogen and heated to 80 ° C. From a dropping funnel 15 ml of a 5 wt .-% solution of 2-hydroxypropyltrimethylammonium hydroxide in 2-ethyl-1,3-hexanediol / methanol (6: 1, parts by weight) are slowly and uniformly added dropwise within 45 minutes. Here, the temperature rises to 88 ° C (90 ° C should not be exceeded, because the trimerization at too high temperatures is nonspecific and leads to higher viscosities of the final product). It is stirred after completion of the dropwise addition at 80 ° C until the reaction mixture has reached an NCO content of 30.6%. Then it is stopped by adding 0.36 g (70 ppm molar) of a 25% solution of dibutyl phosphate in IPDI. Excess monomeric IPDI is removed by thin film distillation. This gives a nearly colorless, clear resin with a yield of 44%, which is dissolved 70% in methyl ethyl ketone. The viscosity of the solution at 23 ° C is 300 mPa-s, the isocyanate content is 11.8% and the content of free, monomeric IPDI is 0.18%.

1.2. Polyisocyanate component A2):

®Desmodur N 3300 (Bayer AG), solids content: 100%; Viscosity at 23 ° C: 3500 mPa · s; Isocyanate content: 21.8%.

Example 2 Preparation of the Inventive Dispersions I) 2.1. Dispersion I.1):

In a 1 l four-necked flask with stirrer, internal thermometer and reflux condenser, 355.93 g of polyisocyanate component A1) are initially charged, dissolved in 411.15 g of methyl ethyl ketone and heated to 60 ° C. Thereafter, 96.13 g of 3,5-dimethylpyrazole are added in portions with stirring. The reaction mixture is stirred at 60.degree. C. until no isocyanate band can be seen in the IR spectrum. Subsequently, 11.51 g of emulsifier WN (emulsifying assistant, Bayer AG) and 5.18 g of ®Synperonic PE / F 127 (emulsifying aid, Fa. ICI) are added and a homogeneous mixture of the components is prepared by stirring. From this solution, a water-in-oil emulsion is prepared by intensive mixing with 359.67 g of water by means of a dissolver, which then by passage through a jet disperser at elevated pressure (10 bar) according to EP 0101007 a phase inversion into an oil in -Water emulsion undergoes. The methyl ethyl ketone is distilled off in vacuo. The dispersion is then filtered through a 10 μm mesh filter. The result is a product with the following characteristics: Outflow time (ISO 4 cup, 23 ° C): 10 s Solids content: 50.3% by weight mean particle size: (laser correlation spectroscopy) 0.42 μm blocked NCO content: (calculated, based on the solids) 11.64%

2.2. Dispersion I.2)

In a 1-liter four-necked flask equipped with stirrer, internal thermometer and reflux condenser 192.66 g of polyisocyanate component A2) are introduced, dissolved in 419.67 g of methyl ethyl ketone and heated to 60 ° C. Thereafter, 87.12 g of butanone oxime under Stirring added in portions. The reaction mixture is stirred at 60 ° C. until the isocyanate band is no longer visible in the IR spectrum. Subsequently, 14.90 g Rhodafac PA 17 (emulsifier, Fa. Rhodia) and 1.20 g of the neutralizing agent triethylamine are added and prepared by stirring a homogeneous mixture of the components. From this solution, a water-in-oil emulsion is prepared by intensive mixing with 195.25 g of water by means of a dissolver, which then by passage through a jet disperser at elevated pressure (1 bar) according to EP 0101007 a phase inversion into an oil in -Water emulsion undergoes. The methyl ethyl ketone is distilled off in vacuo. The dispersion is then filtered through a 10 μm mesh filter. The result is a product with the following characteristics: Outflow time (ISO 4 cup, 23 ° C): 23 s Solids content: 60.0% by weight mean particle size: (laser correlation spectroscopy) 0.36 μm blocked NCO content: (calculated, based on the solids) 14.25%

2.3. Dispersion I.3)

177.96 g of polyisocyanate component A1) and 96.33 g of polyisocyanate component A2) are placed in a 1 l four-necked flask equipped with stirrer, internal thermometer and reflux condenser, dissolved in 447.72 g of methyl ethyl ketone and heated to 50.degree. Thereafter, 113.16 g of cyclohexanone oxime are added in portions with stirring. The reaction mixture is stirred at 50 ° C until no isocyanate band is visible in the IR spectrum. Then 17.70 g of Rhodafac PA 17 (emulsifier, Fa. Rhodia) and 1.67 g of the neutralizing agent N, N-dimethylethanolamine are added and prepared by stirring a homogeneous mixture of the components. From this solution is by intensive mixing with 350.10 g of water by means of a dissolver a water-in-oil emulsion prepared, which then undergoes a phase inversion into an oil-in-water emulsion by passage through a jet disperser at elevated pressure (4 bar) according to EP 0101007. The methyl ethyl ketone is distilled off in vacuo. The dispersion is then filtered through a 10 μm mesh filter. The result is a product with the following characteristics: Outflow time (ISO 4 cup, 23 ° C): 14 s Solids content: 49.6% by weight mean particle size: (laser correlation spectroscopy) 0.36 μm blocked NCO content: (calculated, based on the solids) 14.25%

Example 3 Preparation of base pastes

It describes the preparation of base pastes, as they are commonly used in practice.

3.1. Base paste based on a self-crosslinking polyurethane dispersion (®Bayhydrol VP LS 2153, Bayer AG), consisting of a water-dispersed polyhydroxyl compound and a water-dispersed blocked polyisocyanate (not according to the invention)

For a trituration of 30 minutes in a bead mill, the following components are weighed out and predispersed for about 10 minutes by means of a dissolver: 667.7 parts by weight of the 40% self-crosslinking polyurethane dispersion Bayhydrol VP LS 2153; 4.8 parts by weight of a commercial Antikratermittel; 4.8 parts by weight of a commercial wetting agent; 4.1 parts by weight of an anti-settling agent customary in the paint industry; 10.8 parts by weight of a conventional defoamer for aqueous systems, 118.8 parts by weight of titanium dioxide; 1.3 parts by weight Black iron oxide; 119.7 parts by weight of micronized barite; 29.2 parts by weight of carbonate-free talc and 38.8 parts by weight of distilled water. This results in a paste with a solids content of about 53.6 wt.%.

3.2. Base paste based on the invention-essential dispersion I.2) in combination with an aqueous polyhydroxyl component II) (Bayhydrol® VP LS 2056, Bayer AG) (according to the invention)

The following components are weighed, predispersed for about 10 minutes by means of a dissolver and then ground for 30 minutes in a cooled bead mill: 387.9 parts by weight of the 47% dispersion of the polyhydroxyl compound Bayhydrol VP LS 2056; 237.8 parts by weight of the 60% dispersion I.2); 5.9 parts by weight of a commercial Antikraaermittel; 5.9 parts by weight of a commercial wetting agent; 4.9 parts by weight of an anti-settling agent customary in the paint industry; 13.0 parts by weight of a conventional defoamer for aqueous systems; 143.6 parts by weight of titanium dioxide; 1.6 parts by weight of iron oxide black; 144.7 parts by weight of micronized barite; 35.3 parts by weight of carbonate-free talc and 19.4 parts by weight of distilled water. This results in a paste with a solids content of about 65.0 wt.%.

3.3. Base paste based on dispersion I.3) essential to the invention in combination with an aqueous polyhydroxyl component II) (Bayhydrol® VP LS 2056, Bayer AG) (according to the invention)

The following components are weighed, predispersed for about 10 minutes by means of a dissolver and then rubbed for 30 minutes in a cooled bead mill: 339.9 parts by weight of the 47% dispersion of the polyhydroxyl compound Bayhydrol VP LS 2056; 315.3 parts by weight of the 49.6% dispersion I.3); 5.7 parts by weight of a commercial Antikratermittel; 5.7 parts by weight of a commercial wetting agent; 4.8 parts by weight of a commonly used in the coatings industry Antiabsetzmittels; 12.6 parts by weight of a usual for aqueous systems Defoamer, 139.6 parts by weight of titanium dioxide; 1.5 parts by weight of iron oxide black; 140.6 parts by weight of micronized barite and 34.3 parts by weight of carbonate-free talc. This results in a paste with a solids content of about 63.2 wt.%.

Example 4 Preparation of aqueous fillers based on the base pastes 3.1. to 3.3.

The pastes are mixed homogeneously by dispersing for 10 minutes using a dissolver according to the ratios given in the table below and, if appropriate, adjusted with water to a processing viscosity of ≦ 35 s (ISO cup 5 mm, ISO 2431). The compositions and characteristics of the resulting aqueous fillers are shown in Table 1 below. <u> Table 1 </ u> filler example 1 ¹⁾ 2 ²⁾ 3 ²⁾ 4 ²⁾ 5 ²⁾ Paste 3.1; 53.6% FK * 92.9 parts by weight 52.1 parts by weight 51.9 parts by weight Paste 3.2; 65.0% FK * 98.2 parts by weight 43.0 parts by weight Paste 3.3; 63.2% FK * 100 parts by weight 44.0 parts by weight least. water 7.1 parts by weight 1.8 parts by weight - 4.9 parts by weight 4.1 parts by weight 100 parts by weight 100 parts by weight 100 parts by weight 100 parts by weight 100 parts by weight Solids content 49.8% 63.8% 63.2% 55.9% 55.6% Outflow time, 23 ° C, ISO cup 5 mm 34 s 30 s 18 s 30 s 35 s Flow time, 23 ° C after 14 d at 40 ° C 26 s 30 s 20 s 30 s 31 s *) FK = solids content ¹⁾ not according to the invention ²⁾ according to the invention

The solids contents of the fillers 2 to 5 according to the invention are markedly higher and their viscosity stability after 40 ° C. storage better than that of the high-quality comparative filler 1.

The aqueous filler 1 to 5 were with a commercial flow cup gun with 5 bar air pressure at about 65% rel. Moisture (23 ° C) spray-coated on zinc-phosphated steel sheets coated with a cathodically deposited electrodeposition primer (about 20 microns).

The curing of the filler was carried out after 10 min ventilation at 23 ° C in a convection oven, first 10 min at 70 ° C and then 20 min at 165 ° C. The dry film thickness was about 35 μm.

Table 2 below lists the properties of the fillers <u> Table 2 </ u> filler example 1 ¹ ) 2 ¹ ) 3 ¹ ) 4 ²⁾ 5 ²⁾ Erichsen cupping DIN ISO 1520 10.0 mm 9.0 mm 5.0 mm 10.0 mm 10.0 mm Pendulum hardness DIN 53157 75 s 108 s 136 s 97 s 121 s Gloss 60 ° n. Gardner 64% 73% 77% 65% 70%

The fillers 2 to 5 according to the invention have, in comparison to the commercial filler 1, a very high hardness and a very good elasticity for this hardness. The gloss values of the fillers 2 to 5 according to the invention are at a similar level to the gloss value of the commercial filler 1.

On the filler layers, a commercial automotive topcoat based on alkyd / melamine resin was applied by means of an air-atomizing spray gun with a dry film thickness of about 30 microns and cured at 130 ° C for 30 min.

The most important test results for filler application are summarized in the following table. Not indicated resistance values, e.g. Solvent, water and salt spray resistance, fully meet the requirements of the practice.

Used test methods

• Topcoat level: Measurement of the ripple by means of a Wave Scan measuring device from Byk
• Rockfall resistance : Used as test equipment
  • a) Stone impact tester according to VDA (Erichsen, Model 508) with 2 x 500 g steel shot (edged, 4-5 mm) bombarded with an air pressure of 1.5 bar at 23 ° C. Samples were made for punctures down to the plate (0 to 10, 0 = no punctures, 10 = very many punches).
  • b) Single impact tester ESP-10 according to BMW standard DBP No. 34.31.390 (Byk), the spallings of the filler are measured from the sheet metal in mm.

Topcoat level, measurement by Wave Scan (Byk), (corrected values given)

filler example 1 ¹⁾ 2 ²⁾ 3 ²⁾ 4 ²⁾ 5 ²⁾ shortwave 6.2 6.3 5.4 5.0 4.2 waviness 29.3 26.7 25.3 23.1 19.3

The lower the numerical values for both short and long waviness, the better the topcoat level. The fillers 2 to 5 according to the invention accordingly lead to a better finish level than the comparative filler 1.

Stone impact test

2 times 500 g steel shot, 1.5 bar (characteristic 1-10) filler example 1 ¹⁾ 2 ¹⁾ 3 ¹⁾ 4 ²⁾ 5 ²⁾ VDA multi-layer: characteristic for punctures 2 2 2 2 2 BMW single shot at -20 ° C <1 mm 1.0 mm 1.0 mm <1 mm <1mm

The fillers 4 to 5 according to the invention are at the same high level as the high-quality comparative filler 1, although the fillers according to the invention have a significantly higher hardness. This result is surprising and so unpredictable. The fillers 2 and 3 according to the invention have a slightly worse stone chip resistance.

Summary and discussion of the results

Filler 2 to 5 according to the invention are characterized by a very high solids content and a very high hardness. Therefore, only a low elasticity associated with a poor stone chip resistance and a poor finish paint level were expected. However, the test results clearly show that, contrary to the prior art, the fillers according to the invention have both good elasticity values and very good stone chip resistance and topcoat levels, and are therefore superior to a high-grade, commercially available polyurethane filler. They have an unprecedented level of quality in terms of the entire property spectrum.

Claims (10)

1. Binder mixture for aqueous stoving lacquers composed of

   I) special blocked polyisocyanates dispersed in water,

   II) water-soluble or -dispersible polyhydroxy compounds,

   III) optionally water-soluble or -dispersible crosslinking resins and

   IV) optionally further water-soluble or -dispersible substances,

   
   characterized in that component I consists of:

   A) 40 to 80 wt.% of one or more polyisocyanate components,

   B) 10 to 40 wt.% of one or more monofunctional blocking agents within the context of the isocyanate addition reaction for isocyanate groups,

   C) 1 to 30 wt.% of one or more hydrophilicity agents,

   D) optionally further crosslinking substances,

   E) optionally conventional additives,

   
   with the proviso that component I) has been prepared either by a direct dispersing process or by the phase inversion process by means of a dispersing device with a high dispersing output per unit volume and has an average particle size of the dispersion particles of 0.05 to 10 µm particle diameter, and the binder mixture has a solids content of ≥ 55 wt.%.
2. Binder mixture according to Claim 1, characterized in that as polyisocyanate components A) of component I) use is made of aliphatic and/or cycloaliphatic polyisocyanates containing biuret, isocyanurate, urethane, uretdione, allophanate and/or iminooxadiazinedione groups.
3. Binder mixture according to Claim 1, characterized in that as blocking agents B) of component I) use is made of oximes and/or pyrazoles.
4. Binder mixture according to Claim 1, characterized in that as hydrophilicity agents C) of component I) use is made of external emulsifiers.
5. Binder mixture according to Claim 1, characterized in that polyhydroxypolyesters, polyhydroxypolyethers, polyhydroxypolyurethanes, polyhydroxycarbonates, urethane-modified polyester polyols, urethane-modified polyether polyols, urethane-modified polycarbonate polyols, polymers containing hydroxyl groups, polyester-polyacrylate polyols, polyether-polyacrylate polyols, polyurethane-polyacrylate polyols, polyesterpolyurethanes, polyether-polyurethanes, polycarbonate-polyurethanes, polyether-polyesters or mixtures thereof are used as component (II).
6. Binder mixture according to Claim 1, characterized in that water-soluble or -dispersible blocked polyisocyanates are used as component (III).
7. Binder mixture according to Claim 1, characterized in that water-soluble or -dispersible amino resins are used as component (III).
8. Use of the binder mixtures according to Claims 1 to 7 for the preparation of aqueous stoving lacquers which optionally comprise the conventional auxiliary substances and additives of coating technology.
9. Use of the aqueous stoving lacquer according to Claim 8 for the preparation of filler compositions for metal components.
10. Use of the aqueous stoving lacquer according to Claim 8 for the preparation of filler compositions for car body components.